The present invention relates to a stationary support device for a revolving water drainage wire screen, and particularly for the wire of a paper machine, and particularly relates to means for adjusting and fixing the tilt angle of the drainage surface beneath the wire.
Prior art references bearing on this include:
1. Federal Republic of Germany published application 36 28.282 Al--a Priority Application for reference 3 below, including part of reference 3 plus, in addition, FIGS. 8, 9;
2. Federal Republic of Germany published application 38 00 801 Al--(also part of reference 3);
3. British Application 2 194 257 A, equivalent to U.S. Pat. No. 4,865,692; and
4. U.S. Pat. No. 3,027,940 which was cited in reference 3.
Many of the features described below are known from FIG. 1 of Federal Republic of Germany 38 00 801 Al, which is equivalent FIG. 8 of British Application 2 194 257 A.
Stationary support devices of this type particularly serve for supporting the revolving wire screen on which a fiber web is formed from a fiber suspension which continuously flows onto the wire. The support device has a drainage surface beneath the wire which is on a head ledge. In addition, a scrapper-like front or upstream edge of the head ledge of the support device leads away the so called white water which has passed through the openings of the wire screen and out of the fiber web which is being formed and which adheres to the bottom of the wire At the same time, due to the inclination of the drainage surface of the head ledge relative to the direction of travel of the wire, a vacuum is produced at the bottom of the revolving wire, which increases the drainage. The intensity or rate of this drainage depends on the angle of inclination of the drainage surface.
In paper making machines in which the operating conditions change frequently, for instance, changes of the type of paper being produced, or changes in the speed of operation or the like, a change in the angle of incline of the drainage surface at the stationary support device is frequently necessary. Therefore, for a long time there have been efforts to find a dependable design for changing this angle of incline.
With the above noted known construction, it has been tried, in particular, to make that angle of incline, that is the angle between the drainage surface and the direction of travel of the wire above that surface, reproducible with a high degree of precision. Furthermore, it was desired that the stationary support device be as free of vibration as possible. In order to achieve these goals, as shown, for example, in U.S. Pat. No. 4,865,692, the joint between the leading or front edge of the means on which the drainage surface is defined and the support at the front end region is formed as a spring plate. Furthermore, the clamping element, which clamps together stop surfaces which establish the angle of incline, is developed as an expandable hose The clamping hose acts, on the one hand, so that the joint at the front end or leading end region is under tensile stress and so that, on the other hand, the pair of cooperating stop surfaces that define the tilt angle of the drainage surface are held in continuous contact with each other. The pairs of stop surfaces are formed by at least one wedge rod having a series of wedge sections which cooperate with the other set of stop surfaces to transmit only compressive forces.
One disadvantage of this known construction is that the joint at the front or leading end, which is formed as a spring plate, does not form a precise hinge axis. Upon a change of the angle of incline, the movement of the head ledge cannot be predicted with sufficient assurance. Another disadvantage is that both the moveable support ledge and the rigid support are developed as two C-shaped beams which interleave and engage into each other In this way, heavy parts of complicated shape are necessary, resulting in a relatively high expense of manufacture and a relatively large structural height.
FIGS. 8 and 9 of Federal Republic of Germany published application 36 28 282 Al disclose a tilt angle adjustment device of lesser height, in the form of a C-shaped adjustment ledge, which is under tensile stress. Its manufacture is difficult and costly. Furthermore, there is again a spring plate joint which is under tensile stress.